一种综合固化和桥接性能的堵漏体系

A Lost Circulation Control Slurry with Solidifying and Bridging Functions

针对桥堵浆难以胶结会返吐井筒及触变水泥浆耐漏失压差能力弱,难以有效解决复杂恶性漏失的难题,在对触变水泥浆体系以及桥浆堵漏体系研究的基础上,综合桥浆堵漏和固化堵漏的优点,将二者相结合,研制了一种综合固化和桥接性能的复杂堵漏体系。通过对外加剂的研选,确定了具有良好流变性和触变性的触变水泥浆体系,其中新型触变剂LTA-1的加入对水泥浆稠化时间影响较小,且能增加抗压强度。并通过“狭缝实验”确定桥浆堵漏体系配方。最后根据稠化性能及强度评价,确定该复杂堵漏体系的配方比例为触变水泥浆∶桥浆堵漏体系=2∶1。在满足施工安全的基础上,该堵漏体系能够封堵3~5 mm裂缝块模拟的裂缝性漏失地层和6 mm滚珠模拟的大孔道漏失地层,承压强度大于14 MPa。该体系在满足施工安全的基础上,具有良好的触变性能和堵漏性能,对解决复杂地层的漏失问题起到良好的效果。

Bridging lost circulation control slurries are difficult to be bonded with the walls of leaking channels during mud loss control,and are therefore generally squeezed back into the borehole.Thixotropic cement slurries as a kind of lost circulation material,have low fracture pressure,and are thus incapable of controlling severe mud losses.Based on the studies performed on the thixotropic cement slurries and bridging lost circulation control materials,the two kinds of lost circulation control materials are compounded together to form a new lost circulation control material with the advantages of both.By carefully selecting other additives,a new thixotropic cement slurry with good rheology and thixotropy is formulated.In the new cement slurry,the addition of a new thixotropic agent LTA-1 has only weak effect on the thickening time of the cement slurry,and LTA-1 can improve the compressive strength of the cement slurry.The composition of the bridging lost circulation control slurry is determined through“experiment on a slit”.Based on the requirement of thickening time and strength,the final composition of the lost circulation control slurry is determined to be thixotropic cement slurry∶bridging slurry=2∶1.This lost circulation control slurry can be used to control mud losses through 3–5 mm artificial fractures simulating fractured formations and control mud losses through large pores simulated with 6 mm roller balls.The lost circulation control slurry can form a layer of barrier on the surface of the simulated formations with a pressure bearing capacity of greater than 14 MPa.The use with of this lost circulation control slurry satisfies the need of safe operations.The good thixotropy and lost circulation control capacity of this lost circulation control slurry are of great help to the control of mud losses in drilling complex formations.